Method for determining a setpoint torque for a steering wheel as a function of a gain dependent on a steering wheel torque

Abstract

A method for determining a setpoint torque for a steering wheel of an electric power steering system of a vehicle, the setpoint torque helping determine an engine torque applied directly or indirectly to the steering wheel, the setpoint torque being a function of at least one equivalent lateral acceleration having a dimension of an acceleration, wherein the equivalent lateral acceleration is weighted by a gain dependent on at least a steering wheel torque.

The invention claimed is: 
     
       1. A method for determining a motor torque, comprising:
 determining a setpoint torque for a steering wheel of an electric power steering system, said setpoint torque being a function of at least one equivalent lateral acceleration having a dimension of an acceleration, wherein the equivalent lateral acceleration is weighted by a gain dependent on at least one steering wheel torque and on a vehicle longitudinal speed, 
 determining the motor torque based on the setpoint torque; and 
 applying the motor torque directly or indirectly on the steering wheel. 
 
     
     
       2. The determination method according to  claim 1 , wherein the gain varies between 0 and 1. 
     
     
       3. The determination method according to  claim 1 , wherein the equivalent lateral acceleration depends on a parameter varying depending on a dynamic situation of the vehicle. 
     
     
       4. The determination method according to  claim 3 , wherein the parameter is selected from a yaw rate of the vehicle, a yaw acceleration of the vehicle, a lateral acceleration of the vehicle, a steering wheel angle, a force being exerted on a rack, the force being measured by means of a sensor which is positioned on the rack, an estimated force being exerted on the rack, the estimated force comprising an estimate of the friction being exerted on the electric power steering system, or a desired force being exerted on the rack. 
     
     
       5. The determination method according to  claim 1 , wherein the setpoint torque is a function of a total equivalent lateral acceleration dependent on a plurality of equivalent lateral accelerations. 
     
     
       6. The determination method according to  claim 3 , wherein the total equivalent lateral acceleration is calculated by a weighted average of the plurality of the equivalent lateral accelerations.